This is a working overview of Enkephalinase, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-04-14. Anything still debated is marked as such rather than presented as settled.
Published clinical evidence is limited. Most controlled trials were conducted in Russia, enrolled modest numbers of participants, and appeared in Russian-language journals, which restricts independent verification. Reported outcomes include lower anxiety scores, improved attention and memory measures, and changes in fatigue ratings. Reviews written in English note methodological limitations such as small samples and inconsistent endpoints. Whether the compound produces clinically meaningful benefit relative to established anxiolytics is therefore an open question rather than an established finding.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. It was designed at the Institute of Molecular Genetics of the Russian Academy of Sciences as a structural analogue of tuftsin, a naturally occurring tetrapeptide fragment of the immunoglobulin heavy chain. The added Pro-Gly-Pro tail was intended to slow enzymatic degradation and extend biological activity. In Russia it is registered as an anxiolytic nasal preparation, while regulators elsewhere have not approved it for clinical use.
Naming conventions place Selank in the same research family as Semax, another Russian-developed peptide investigated for cognitive effects. The two compounds share a lineage but differ in sequence and in the biological systems proposed as their targets. Semax descends from ACTH fragments, whereas Selank descends from tuftsin. Publications sometimes identify Selank by its full peptide sequence or by laboratory codes rather than one uniform trade name. Because replication outside Russia is limited, reports on its properties are best read alongside the study design and the purity of the material tested.
Selank is a synthetic heptapeptide developed in Russia during the 1990s. Researchers at the Institute of Molecular Genetics of the Russian Academy of Sciences designed it as a stabilized analog of tuftsin, a naturally occurring immunomodulatory tetrapeptide. The compound has been studied primarily for its reported anxiolytic and nootropic effects. It remains largely unknown in Western pharmacology and is not approved as a medicine by major regulators such as the FDA or the EMA.
The primary structure of Selank is Thr-Lys-Pro-Arg-Pro-Gly-Pro, corresponding to the molecular formula C33H57N11O9 and a monoisotopic mass of roughly 751.9 daltons. The N-terminal threonine and the arginine residue in the fourth position are shared with tuftsin, which carries the sequence Thr-Lys-Pro-Arg. The three additional residues at the C-terminus, Pro-Gly-Pro, extend the chain and are associated with greater resistance to enzymatic degradation. This extension also separates Selank from the shorter parent peptide.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C33H57N11O9 | Free peptide form |
| Molecular mass | About 751.9 Da | Calculated average mass |
| Amino acid sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Single-letter form TKPRPGP |
| Structural basis | Tuftsin analogue | Extended version of a natural tetrapeptide |
| Development origin | Russian Academy of Sciences | Work carried out from the 1980s onward |
Pharmacokinetic data are limited. Like most short peptides, Selank is vulnerable to plasma and tissue peptidases, and its measured half-life in circulation is short, on a minutes scale. The Pro-Gly-Pro tail slows this degradation but does not eliminate it. Intranasal administration is the route described in most reports, with absorption through the nasal mucosa and a hypothesized path into the central nervous system that avoids the blood-brain barrier. Direct measurements of human brain exposure are unavailable, so distribution claims rest on inference from animal work.
Clinical evidence comes mainly from small studies conducted in Russia, several of which were open-label or lacked robust blinding. Reported outcomes include lower anxiety scores, changes in attention measures, and effects on asthenic states following illness. Sample sizes are typically in the tens of participants, and independent replication outside the region is scarce. Reviews published in English generally note the limited methodological quality of the underlying trials. Whether the compound produces clinically meaningful effects under rigorous conditions remains unresolved.
Proposed mechanisms center on modulation of the GABA system, but no single molecular target has been confirmed. Rodent studies report changes in GABA-A receptor expression and in the turnover of serotonin, dopamine, and norepinephrine in several brain regions. Increases in brain-derived neurotrophic factor and its receptor have also been described after repeated administration. These findings come largely from animal models, and the degree to which they describe human neurochemistry remains an open question. The mechanism is best characterized as multi-system and not fully resolved.
Peptide bonds are vulnerable to protease attack, and Selank is no exception. Measured half-life in serum is short, on the order of minutes in several reports, which explains why intranasal administration is the common route described in the literature. Absorption across the nasal mucosa partially bypasses first-pass hepatic metabolism. Quantitative data on human bioavailability remain limited and are difficult to compare across studies.
Lyophilised material kept dry at minus 20 degrees Celsius or colder is the most stable form, and suppliers commonly state a shelf life of two years or more under those conditions. Once dissolved, degradation accelerates through hydrolysis and deamidation, particularly at alkaline pH or elevated temperature. Working solutions are usually divided into single-use aliquots to avoid repeated freeze-thaw cycles. The choice of reconstitution solvent affects both stability and the ionic strength of the final preparation.
Once dissolved, the peptide is markedly less stable than the dry powder. Aqueous solutions are subject to backbone hydrolysis and to microbial growth when they are handled without sterile technique. Buffered solutions near neutral pH are common for short-term laboratory work, while acidic conditions are sometimes used to improve solubility. Analytical laboratories generally prepare working solutions fresh rather than storing them, and a residual water film left in a reopened vial can seed degradation even when the container appears dry.
Reversed-phase high-performance liquid chromatography is the standard technique for estimating peptide purity. The result is a peak-area percentage, which describes how much of the detected material elutes as the main peak in one run. Mass spectrometry confirms the molecular mass and can reveal truncated, adducted, or otherwise modified species. Amino acid analysis or tandem mass spectrometry can address sequence fidelity when identity is in doubt. None of these measurements, taken alone, establishes that a sample is fit for any specific purpose.
=== Side effects === Citicoline has a very low toxicity profile in animals and humans. Clinically, doses of 2000 mg per day have been observed and approved. Minor transient adverse effects are rare and most commonly include stomach pain and diarrhea.
== Overview == Platelet-mimicking particles, an innovation of drug delivery since the mid-twentieth century, are designed to mimic the functionality of natural platelets, with ongoing research focusing on optimizing their biocompatibility, clot integration, and targeted delivery capabilities. Advances in nanotechnology and molecular engineering have enabled the development of platelet-mimicking drug delivery systems. Current research aims to replicate key platelet functions such as adhesion, aggregation, and clotting to enhance hemostatic responses and targeted therapies. Primary synthetic platelet preparations involve nanoscale polymeric architectures, peptides, or extracellular vesicles to improve biocompatibility and therapeutic efficacy. Current iterations of synthetic platelets - hydrogel-based nanoparticles that mimic the size, mechanics, and shape of natural platelets - have demonstrated efficacy in promoting clotting and wound healing in preclinical studies involving rodents and pigs. Originally designed to improve patient outcomes related to hemostasis, synthetic platelets are now being explored in other therapeutic areas including immune modulation and anticancer treatment. For example, a recent platelet design engineered for anticancer treatment can be freeze-dried and rehydrated when needed, offering a longer shelf life compared to natural platelets, which typically degrade rapidly when stored.
7α-Acetylthio-17α-hydroxy-3-oxopregn-4-ene-21-carboxylic acid γ-lactone 7α-Acetylthio-3-oxo-17α-pregn-4-ene-21,17β-carbolactone 3-(3-Oxo-7α-acetylthio-17β-hydroxyandrost-4-en-17α-yl)propionic acid lactone 7α-Acetylthio-17α-(2-carboxyethyl)androst-4-en-17β-ol-3-one γ-lactone 7α-Acetylthio-17α-(2-carboxyethyl)testosterone γ-lactone
These sickle-shaped cells cannot carry nearly as much oxygen as normal red blood cells and they get caught more easily in the capillaries, cutting off blood supply to vital organs. The single nucleotide change in the beta-globin means that even the smallest of exertions on the part of the carrier results in severe pain and even heart attack. Below is a chart depicting the first thirteen amino acids in the normal and abnormal sickle cell polypeptide chain.
where εr is the relative permittivity of the medium, εo is the permittivity of vacuum, R is the universal gas constant, T is the absolute temperature, c is the molar concentration, and F is the Faraday constant When an electric field is applied to the fluid (usually via electrodes placed at inlets and outlets), the net charge in the electrical double layer is induced to move by the resulting Coulomb force. The resulting flow is termed electroosmotic flow. In CEC positive ions of the electrolyte added along with the analyte accumulate in the electrical double layer of the particles of the column packing on application of an electric field they move towards the cathode and drag the liquid mobile phase with them. The relationship between the linear velocity u of the liquid in the capillary and the applied electric field is given by the Smoluchowski equation as
Sources: en.wikipedia.org
A critical step in T cell maturation is making a functional T cell receptor (TCR). Each mature T cell will ultimately contain a unique TCR that reacts to a random pattern, allowing the immune system to recognize many different types of pathogens. This process is essential in developing immunity to threats that the immune system has not encountered before, since due to random variation there will always be at least one TCR to match any new pathogen. A thymocyte can only become an active T cell when it survives the process of developing a functional TCR. The TCR consists of two major components, the alpha and beta chains. These both contain random elements designed to produce a wide variety of different TCRs, but due to this huge variety they must be tested to make sure they work at all. First, the thymocytes attempt to create a functional beta chain, testing it against a 'mock' alpha chain. Then they attempt to create a functional alpha chain. Once a working TCR has been produced, the cells then must test if their TCR will identify threats correctly, and to do this it is required to recognize the body's major histocompatibility complex (MHC) in a process known as positive selection. The thymocyte must also ensure that it does not react adversely to "self" antigens, called negative selection. If both positive and negative selection are successful, the TCR becomes fully operational and the thymocyte becomes a T cell.
Jung proposed that art can be used to alleviate or contain feelings of trauma, fear, or anxiety and also to repair, restore, and heal. In his work with patients and his own personal explorations, Jung wrote that art expression and images found in dreams could help recover from trauma and emotional distress. At times of emotional distress, he often drew, painted, or made objects and constructions, which he recognised as more than recreational. He also encouraged his patients to paint their psychic images.
==== Chlorophylls ==== Chlorophyll a is found in all chloroplasts, as well as their cyanobacterial ancestors. Chlorophyll a is a blue-green pigment partially responsible for giving most cyanobacteria and chloroplasts their color. Other forms of chlorophyll exist, such as the accessory pigments chlorophyll b, chlorophyll c, chlorophyll d, and chlorophyll f. Chlorophyll b is an olive green pigment found only in the chloroplasts of plants, green algae, any secondary chloroplasts obtained through the secondary endosymbiosis of a green alga, and a few cyanobacteria. It is the chlorophylls a and b together that make most plant and green algal chloroplasts green. Chlorophyll c is mainly found in secondary endosymbiotic chloroplasts that originated from a red alga, although it is not found in chloroplasts of red algae themselves. Chlorophyll c is also found in some green algae and cyanobacteria. Chlorophylls d and f are pigments found only in some cyanobacteria.
=== Tigrayan Opposition Parties === Opposition groups inside Tigray strongly rebuked the TPLF's actions. On May 11, Salsay Weyane Tigray (Sawet) issued an official statement rejecting the council's return, characterizing the assembly as a "theatrical performance" disconnected from legality and morality. The party accused the TPLF of treating the historical suffering of Tigrayans as a political tool to retain a three-decade monopoly on power. Sawet demanded an immediate halt to the political gamble and called for the creation of an all-inclusive Interim Transitional Government representing alternative civil and political stakeholders.
Sources: en.wikipedia.org
It is a seven-amino-acid peptide, Thr-Lys-Pro-Arg-Pro-Gly-Pro, produced by chemical synthesis rather than extracted from biological tissue. Its design is based on tuftsin, a natural immunomodulatory tetrapeptide. The C-terminal Pro-Gly-Pro segment is a common stabilising motif in short regulatory peptides.
The core four residues correspond to tuftsin, which occurs naturally as part of immunoglobulin G. The full seven-residue sequence, however, is not a known endogenous peptide. It is a laboratory-designed analogue intended to combine tuftsin-like activity with greater resistance to breakdown.
No single receptor has been confirmed as the primary target. Reports describe involvement of the GABAergic system, interference with enkephalin degradation, and shifts in neurotrophic factor expression. Because these observations come from different models and assays, they have not yet been integrated into one accepted mechanism.
Selank is a synthetic heptapeptide designed as a stabilized analog of the natural tetrapeptide tuftsin. It has been investigated mainly for anxiolytic and cognitive effects. It is not an approved pharmaceutical in most countries.